This application is based upon and claims the benefit of Japanese Patent Application No. 2000-333302 filed on Oct. 31, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a cooling device for cooling a heat-generating member such as a semiconductor device by boiling and condensing refrigerant.
2. Description of Related Art
In recent years, due to a demand for portable terminals and the like, there has been a need for cooling devices which can be used in any attitude. Also, with a remarkable improvement of a processing in a personal computer, a heat amount emitted from a semiconductor integrated circuit such as a CPU is increased. Thus, miniaturization and high efficiency are demanded for the cooling devices.
In order to meet such a need, in a cooling device of JP-A-10-209355, JP-A-10-209356 or JP-A-11-87583, a refrigerant tank is formed from a sealed tank having a pair of faced walls, a heat-generating member (CPU) is fixed on one (heat-receiving wall) of the faced walls of the sealed tank, a radiation fin is fixed on the other one (radiation wall) of the faced walls, and a predetermined amount of refrigerant is stored in the sealed tank. In a side situation where the CPU is mounted on a side wall of the sealed tank (i.e., the faced walls described above are arranged vertically), a liquid surface of the refrigerant in the tank may become lower than a mounting portion of the CPU. Thus, in some cooling devices, a main wick (porous metallic sintered body) for transporting liquid refrigerant to a portion corresponding to the mounting position of the CPU by a capillary action is provided in the tank. In addition, in order to improve a cooling capacity of the cooling device, a condensation fin is provided on an inner surface of the radiation wall (condensation plane) so that heating-transmitting area (condensing area) is increased. However, in this case, liquid refrigerant readily stays in a lower side of the condensation fin and clearances of the condensation fin due to a surface tension of liquid refrigerant. Accordingly, the condensing area of gas refrigerant can not be effectively increased, and a sufficient cooling capacity can not be obtained.
In view of the foregoing problems, it is an object of the present invention to provide a cooling device in which a main wick and an auxiliary wick are disposed in a tank to improve cooling capacity.
According to an aspect of the present invention, in a cooling device, a main wick, for transporting liquid refrigerant to an attachment area of a heat-generating member in a tank, is provided on an inner surface of a heat-receiving wall of the tank, a plurality of condensation fins are disposed on the radiation wall in the tank, and an auxiliary wick is disposed in the tank for connecting the main wick and the condensation fins. The auxiliary wick is arranged at least opposite to a part of the attachment area of the heat-generating member. Therefore, a vapor refrigerant boiled in the tank within attachment area can flow toward around the auxiliary wick, and flows vapor passages between adjacent condensation fins. Therefore, the vapor refrigerant is liquefied on the condensation fins, and condensed liquid refrigerant is readily transported to the main wick through the auxiliary wick. Accordingly, the refrigerant can efficiently circulate in the refrigerant tank without being disturbed by the auxiliary wick.
Preferably, the auxiliary wick is disposed to opposite to a center line of the attachment area. More preferably, the auxiliary wick extends in the tank from one end to the other end. Accordingly, vapor refrigerant can be readily introduced into the condensation fins on both sides of the auxiliary wick without being affected by the auxiliary wick, and condensed liquid refrigerant can be readily introduced into the main stack through the auxiliary wick.
According to an another aspect of the present invention, a main wick is disposed in the tank to contact the heat-receiving wall, and an auxiliary wick for connecting the main wick and the condensation fins is disposed at an end of the closed space in the tank. Therefore, vapor refrigerant boiled by receiving heat from the heat-generating member is readily flows from the main wick to the condensation fins without being affected by the auxiliary wick, and condensed liquid refrigerant on the condensation fins can be readily introduced into the main wick through the auxiliary wick.